It is not only not permitted to use the mobile phone while driving, but it is also a danger to life. You endanger yourself and others. The legal - and much more comfortable - solution is to use a hands-free-kit, which is simply fastened to the sun visor.
Don’t risk anything!
No drilling, raw plugs or screwing. Simply fitted to the sun visor, the light weight allows to phone, just like the police allows it to.